The long-term objective of the proposed MIND-USA (Modifying the Impact of ICU-Induced Neurological Dysfunction-USA) Study is to define the role of antipsychotics in the management of delirium in vulnerable critically ill patients. We and others have shown that delirium is an independent predictor of more death, longer stay, higher cost, and long-term cognitive impairment often commensurate with moderate dementia. The rapidly expanding aging ICU population is especially vulnerable to develop delirium, with 7 of 10 medical and surgical ICU patients developing this organ dysfunction. Antipsychotics are the first-line pharmacological agents recommended to treat delirium, and over the past 30 years they gained widespread use in hospitalized patients globally prior to adequate testing of efficacy and safety for this indication. Haloperidol, the most commonly chosen antipsychotic, is used by over 80% of ICU doctors for delirium, while atypical antipsychotics are prescribed by 40%. Antipsychotics safety concerns include lethal cardiac arrhythmias, extrapyramidal symptoms, and the highly publicized increased mortality associated with their use in non-ICU geriatric populations. The overarching hypothesis is that administration of typical and atypical antipsychotics-haloperidol and ziprasidone, in this case-to critically ill patients with delirium will improve short- and long-term clinical outcomes. Aim 1 will determine whether haloperidol or ziprasidone will increase days alive without acute brain dysfunction (referred to as delirium/coma-free days or DCFDs) over a 14-day period compared with placebo and compared to one another. Aim 2 will determine whether haloperidol or ziprasidone will improve 30-day, 90-day, and 1-year survival compared with placebo and compared to one another. Aim 3 will determine whether haloperidol or ziprasidone will reduce ICU length of stay compared with placebo and compared to one another. Aim 4 will determine whether haloperidol or ziprasidone will reduce the incidence, severity, and/or duration of long-term neuropsychological dysfunction and improve quality of life at 90-day and 1-year follow-up compared with placebo and compared to one another. To address these Aims, we will conduct this multi-center, double blind, randomized, placebo-controlled investigation in 876 critically ill, delirious medical/surgical ICU patients who are (a) on mechanical ventilation or non-invasive positive pressure ventilation or (b) in shock on vasopressors. In each group (haloperidol, ziprasidone, and placebo), 292 patients will be enrolled and treated until delirium has resolved for 48 hours or to 14 days (whichever occurs first) and followed for 1 year. We will monitor many safety parameters such as cardiac dysrhythmias and extrapyramidal symptoms. This study will have adequate power to detect the effect of antipsychotics in 4 important subgroups including age >65 years, severity of illness (APACHE II > 25), severe sepsis at enrollment, and medical vs. surgical ICU patients, and a hypothesis generating analysis of patients with pre- existing cognitive impairment.